Keeping your movie projector's film path clean is vital to prevent scratching of your precious film prints and also to extend the life of your machine.  In addition to using a soft camel hair brush to free debris...finish up by using Dust Off Compressed Air after every reel to get rid of any dust left behind that could scratch your prints....especially around the film gate.  No film collector should be without at least two cans...so you always have that spare in case you run out.  Do not use Dust Off for delicate film lenses. For cleaning lenses, always use Tiffen Lens Cleaner and Lens Cleaner Paper.